Flash copper coating



Patented Mar. 15, 1938 UNITED STATES men oorrcn. COATING Earl T. Alvord, Cleveland Heights, Ohio, asaignor,

by mesne assignments, to E. I. du Pont de Nemours &- Company, W

ration of Delaware n, DeL, a corpo- No Drawing. Application December 12, 1935,

Serial No. 54,151

1 Claim. (01. 91-683) This invention relates to the flash copper coating of iron or steel articles, and is particularly directed to the use of inhibitors in flash copper coating from acid solutions.

5 Iron, of course, is above copper in the electromotive force series of metals and will replace it in its salts. This principle has been utilized in a method of coating iron with a thin copper film, wherein it has been the practice to immerse the iron in an acid solution of a copper salt.

I have found that a more adherent and brighter copper coating may be obtained if the copper salt baths employed contain a small amount of an acid inhibitor.

i5 Acid inhibitors are, of course, a well known class of materials. They are ordinarily used in metal pickling to restrain the action of acids upon steel without substantially interfering with the removal of scale and other undesirable incrustago tions. As typical inhibitors suitable for use according to my invention, 1 may mention the following: aldehydes, such as furfural; aldehyde derivatives, such as the condensation products of aldol with alpha naphthylamine; organic sulfides of the type RzN-CS-SrCS-NRz, such as thiuram sulfide; mercaptans, such as dithiotrimethylene mercaptan; saturated heterocyclic compounds containing at least three difierent atoms in the ring, two of the atoms preferably being nitrogen and carbon, such as parahydroxy-N-phenyl morpholine; thiocyanates, such as lauryl pyridinium thiocyanate; mustard oils, such as allyl isothiocyanate; cinchona bark alkaloids and their derivatives, such as sulfurized quinoidine; thioureas, such as di-ortho-tolyl thiourea; aldehyde mercaptyls; sulfonated oils, such as ichthyol; thiazoles, such as anilinobenzthiazole; thioglycollic acid and its derivatives, such as ethyl thioglycollic acid and diphenyl thiohydrantoin; pc-

troleum oil residues and waste acids; extracts from destructive distillation of carbonaceous matter; oil refinery waste; and pyridine bases. My invention may be better understood by reference to thefollowing examples: i5

ExampleI A bath for flash copper coating was prepared using sulfuric acid in an amount required to pro-.

55 for a P riod of ten minutes. At the nd of this time the sheet was withdrawn and washed in water. A smooth and bright coating of copper was produced on the surface of the steel, and, by comparing the plate with one flash copper coated in a similar bath which contained no 5 inhibitor, it was observed that the coating obtained by the process of this example was brighter and more adherent.

Example II A bath similar to that of Example I for the deposition of copper by immersion was prepared with one and two-tenths per cent of copper sulfate (CuSO4) and with an amount of sulfuric acid I suflicient to provide four per cent by weight free 15 H2504. To the bath was added 0.0125% of an inhibitor comprising a condensation product of crotonaldehyde aldehyde and ammonium sulfide. The bath had a density of about nine degrees B. Steel wire which was free from scale was im- 20 mersed in the bath and permitted to remain for ten minutes. At the end of this time the wire was transferred to an alkaline wash made with dilute sodium hydroxide. A bright and adherent copper coating was produced on the wire by 2 this procedure. 7

It will be understood that various copper salts and various acids may be used in the preparation of baths for the coating of copper by immersion in accordance with known practice. It'will also 30 be understood that the acidity of the bath may vary considerably depending upon the character of the steel being treated. Ordinarily, it is the practice to have between about four and twenty per cent free H2804 present. 35

The time required to produce a satisfactory coating will necessarily vary considerably with the specific bath composition and, in accordance with known practice, the work must be left in the bath for longer periods as the solution becomes 0 exhausted.

The quantity of inhibitor used may be widely varied, but it is generally desirable to use a little less of the inhibitor than would be used for maximum efficiency in an acid pickling bath. 4 The inhibitor used in Example II is of veryhigh maximum efiiciency, and the results obtained were not as good as those achieved with the slightly less efiicient inhibitor of Example I. Ordinarily, then, a moderately efiicient inhibitor may best be used, or a very efiicient inhibitor may be used in a restricted amount, the amount and. type of inhibitor being selected so that if used in anacid pickling bath the dissolution of steel would be considerably, tho not entirely, prevented, say 80 to 90% .less than ii no inhibitor were used. It will be understood, of course, that larger or smaller mounts of inhibitor may be used to produce results advantageous over the prior art.

It is not understood exactly what action the inhibitor has. Some otthe improvement in results may be attributable to the restraining action or the inhibitor, but this action would not be expected/to produce brighter and more adherent That it is not solely the lncopper coatings. hibiting function of the inhibitor which leads to my improved results is evidenced by the fact that for my purposes exceedingly high efllciencies arenot as advantageous as slightly lower eiilciencies.

While I have shown a number or specific compositions and inhibitors above. it will be understood that I do not intend to be limited thereto as one skilled in the art may readily produce a number of baths for flash copper coating without departing from the spirit of my invention. The essential feature of my invention is the use 01' an inhibitor in an acidic bath for the deposition oi copper by immersion.

I claim:

In a process for the deposition oi-copper by immersion, the step comprising subjecting a terrous article to a sulfuric acid solution of copper sulfate which contains a small amount of an organic acid-inhibitor of the type used to restrain the action of acids upon steel. I EARL '1'. ALVORD. 

